Generally, a dust collector is an apparatus which collects and removes gaseous or liquid fine particles floating in gas. In the first place, the dust collector was used to remove fine particles of ash contained in flue gas of a boiler. Recently, the dust collector is mounted on many chimneys of a factory to prevent sooty smoke and other fine particles from coming out of the chimneys. The fine particles have a size of about 1 mm to 1 μm. Relatively large particles can be easily removed, but it is difficult to remove fine particles which may have a bad influence on a human body. Dust collecting methods include a method using gravity, a filtering method using filter media, a method using inertia or a centrifugal force, a method using sound waves, a cleaning method and the like, and may be largely classified into mechanical methods and electrical methods. The mechanical methods include a dry method and a wet method.
The dust collector which filters contaminated gas to clean the gas is widely used in order to remove fine particles of ash in sooty smoke and also to improve the environment in a factory or a work place equipped with various facilities.
Among the dust collectors, a filter dust collector is an apparatus for separating particles such as dust from gas by passing the gas containing the particles through various filter media and is referred to as a filter dust collecting apparatus. The filter dust collector is one of air pollution prevention apparatuses which filter various particles in air causing air pollution or noxious particles contained in discharge gas of a factory or the like, or prevent such particles from being discharged. As for a filtering method, there are a surface filtering method in which dust is attached to the surface of a filter medium such as thin paper or fibers and an inner filtering method in which dust is collected in a fibrous layer of a bag filter which is a filter cloth formed in a bag shape or a flat plate shape using a filter medium having a thick layer such as glass fibers or cotton fibers.
In the filter dust collector, dust is separated only by a filtering effect of the filter medium in an initial operation, but a dust layer, which is accumulated on the surface of the filter medium as time goes by, is closely filled in holes of the filter medium, thereby increasing removal efficiency. Generally, in a case of dust having a size of 1.0 μm or more, it provides efficiency of 99% or more. This apparatus collects dust on the principles such as impact, direct interception, surface deposition, and diffusion.
However, if the dust accumulated on the surface of the filter medium is excessively thick, an amount of air passing through the filter medium is reduced and the holes of the filter medium may be clogged with dust. In this case, since the filter medium cannot be used, replacement should be performed. Accordingly, after the filter medium is used for some time, a removal operation should be performed to remove the dust accumulated on the surface of the filter medium. Removal methods include an intermittent method and a consecutive method. The intermittent method is a method for removing dust by dividing a dust collecting room into three or four portions and intercepting flow of gas only at a portion where the pressure loss reaches a predetermined value. The consecutive method is a method for removing dust by continuously collecting dust to sequentially remove dust attached to the filter medium without division of the dust collecting room or interception of gas.
The filter dust collectors which perform a removal operation include a vibration type filter dust collector, a backflow type filter dust collector, and an impact ejection type filter dust collector. The vibration type filter dust collector uses sound waves or vibrates vertically and laterally, and the counter air flow type filter dust collector supplies compressed air in a reverse direction while filtration is performed to remove dust attached to the inside of the filter cloth. The impact ejection type filter dust collector supplies compressed air inside the filter cloth in order to remove dust attached to the outside of the filter cloth, thereby instantaneously removing the dust. A dual impact ejection type filter dust collector is widely used.
However, according to the conventional impact ejection type filter dust collector, it is necessary to eject high-pressure compressed air to the filter cloth to efficiently remove the dust accumulated to the filter cloth. In this case, very large noise is generated to damage the work environment. Further, when the compressed air is ejected to the filter cloth to remove dust of the filter cloth, the amount of dust entering in the filter cloth through attraction holes is reduced since the direction of the compressed air entering into the dust collector is opposite to the dust injection direction. Consequently, a large-capacity pump should be used to make the amount of dust entering in the filter cloth through attraction holes equal to the amount when the compressed air is not supplied, thereby increasing the manufacturing costs. Meanwhile, the dust collecting operation is stopped and the removal operation is performed to prevent backflow of dust coming through the attraction holes, but in this case, air purification performance is reduced.